1. Field of the Invention
The invention relates in general to elevator systems, and more specifically, to elevator systems which have a plurality of traveling cables.
2. DESCRIPTION OF THE PRIOR ART
The operation of an elevator car requires a large number of control and signal wires between the elevator car and elevator control located in the machine room. Electrical power for car lighting fixtures and fans is supplied to the car, as well as electrical power for operating car mounted control. Control signals from car mounted switches and sensors must be sent to the machine room, as well as car calls entered on the call station. Control signals, such as car call resets and remotely set car calls must be sent to the elevator car. In addition to the functional control and signal wires, it is common to provide at least four spare control wires and four spare signal wires. If voice communication between the elevator car and a remote communication point is required, additional wires for such communication are provided.
The control and signal wires are assembled together into a traveling cable which extends from a junction box on the bottom of the elevator car to a junction box in the hoistway which is usually located at the midpoint of the elevator car travel path. The traveling cable is suspended from the bottom of the car such that it forms a loop below the car, with the bight of the loop moving with vertical movement of the car. When the traveling cable exceeds a length of about 100 feet, the weight of the cable is supported by a steel strand which is added to the traveling cable, with the ends of the steel strand being separately mounted on the car and in the hoistway.
The traveling cable is free to swing pendulum fashion due to car movement, bending of the traveling cable in the bight, and to air currents in the hoistway, and the prior art has used different arrangements for protecting the traveling cable from damage which may occur if the traveling cable contacts structural members in the hoistway. For example, U.S. Pat. No. 3,430,733 discloses a split, flexible protective tube which is snapped about the traveling cable at locations which might contact structural members in the hoistway. U.S. Pat. No 3,344,888 guides the traveling cable in a separate vertical chute having a slot therein.
The traveling cable must be flexible in order to bend properly in the bight which moves as the car moves. In high rise buildings, the total weight of the traveling cable increases, and the number of control and signal wires may also increase, necessitating a plurality of separate traveling cables in order to provide the desired cable flexibility. It has been found that the bights or bottom portions of the loops of the plurality of traveling cables do not stay in line as one might expect, but exhibit an erratic movement with respect to one another, often resulting in entanglement with other items in the hoistway, such as with the compensation cables, as well as causing undesirable contact with structural members and hoistway mounted equipment. A special traveling cable chute is very costly for high rise buildings, and protective tubes would not prevent entanglement of the plurality of traveling cables with the compensation cables.